Implants for delivering a beneficial agent such as a drug are known to the prior art in Remington's Pharmaceutical Sciences, 4th Ed., pp 1714-17, (1970) published by the Mack Publishing Company. Generally, the implants known to the prior art comprise a nonerodible matrix, an erodible matrix, or a capsule. More specifically, the nonerodible matrix implant comprises a drug dispersed in a polymer. A drug is released, when the matrix implant is in an aqueous biological environment, by diffusing from the implant, or the drug is leached from the implant. This implant initially releases a drug at a constant rate followed by a rate that declines over time. An erodible implant generally comprises a drug dispersed in a polymer that dissolves or erodes in body fluids. As this implant loses its physical and chemical integrity, it exhibits an accompanying decrease in the rate of drug delivery over time. Capsule implants are made with an erodible or a nonerodible wall, and in the former manufacture it releases the drug instantly, and in the latter it releases the drug in a declining rate over time.
In view of the above presentation, it will be self-evident to those versed in the implant art that a pressing need exists for an implant which is biocompatible and releases a beneficial agent at a constant and predetermined rate over time. The need exists for an implant manufactured as an implantable dispenser useful for delivering, for example, steroids, peptides and other agents which would benefit a host therapeutically from long duration implantation. It will be appreciated that if a novel implantable delivery dispenser is made available that possesses the kinetic ability to deliver a beneficial agent at a controlled rate over time, such an implantable delivery dispenser would have a practical application in the fields of human and veterinary medicine.